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IC 9125 



Bureau of Mines Information Circular/1987 



Respirable Dust Levels in Coal, Metal, 
and Nonmetal Mines 



By W. F. Watts, Jr., and D. R. Parker 




UNITED STATES DEPARTMENT OF THE INTERIOR 



Information Circular 9125 



Respirable Dust Levels in Coal, Metal, 
and Nonmetal Mines 



By W. F. Watts, Jr., and D. R. Parker 



UNITED STATES DEPARTMENT OF THE INTERIOR 
Donald Paul Hodel, Secretary 

BUREAU OF MINES 
Robert C. Horton, Director 







Library of Congress Cataloging in Publication Data: 



Watts, W. F. (Winthrop F. Jr) 

Respirable dust levels in coal, metal, and nonmetal mines. 



(Information circular ; 9125) 



Bibliography: p. 18. 

Supt. of Docs, no.: I 28.27: 9125. 



1. Mine dusts- United States- Standards. 2. Coal mines and mining- United States- Dust 
control -Standards. I. Parker, D. R. (Douglas R.) II. Title. III. Series: Information circular 
(United States. Bureau of Mines); 9125. 

4^295JI4^" [TN312] 622 s [363.1'19622] 86-600380 



CONTENTS 



Page 



Abstract 1 

Introduction • 

MIDAS metal and nonmetal subsystem 

Regulatory requirements 

Data description 2 

Software ••• 3 

MIDAS coal subsystem 4 

Regulatory requirements 4 

Data description 4 

Software 5 

Respirable dust analysis 5 

Metal and nonmetal « 5 

Exposures by mine type and occupation 6 

Effect of changing the RQ standard 8 

Coal 9 

Summary and conclusions 17 

References . 18 

Appendix. — MSHA sampling codes, descriptors, and selected data 19 

ILLUSTRATION 

1. Logarithmic probability plots of longwall, continuous ripper, and auger 

samples grouped by designated occupation and nondesignated occupation... 13 

TABLES 

1. Contaminants most frequently sampled in metal and nonmetal mines 3 

2. Yearly statistics for RQ 6 

3. RQ exposures by mine type for 1974-79 and 1980-84 7 

4. RQ exposures by metal and nonmetal occupation for 1974-79 and 1980-84.... 8 

5. Quartz statistics for selected commodities 9 

6. Effect of changing the RQ TLV 10 

7. Yearly trends in respirable dust exposure for samples collected in under- 

ground coal mines 11 

8. 1984 coal dust data by underground mining method 11 

9. Differences between DO and NDO samples for three mining methods 12 

10. Average number of samples exceeding 2.0 mg/nr 5 for 1981-84 and average 

number of mines with samples exceeding 2.0-mg/ra- 5 standard 14 

11. 1984 coal mine dust data for underground and surface occupations 15 

12. Trends in exposure for five underground coal mine occupations 16 

A-l. Metal and nonmetal occupation codes 20 

A-2. Metal and nonmetal location codes 20 

A-3. Metal and nonmetal SIC codes 21 

A-4. Occupation codes most frequently used in 1984 by MSHA coal mine 

inspectors 22 

A-5. MSHA coal mine codes for mine type 22 

A-6. MSHA coal mine codes for sample type 23 

A-7. MSHA coal mine codes for mining method 23 

A-8. Percentage of metal and nonmetal miners wearing respirators 23 

i 





UNIT OF MEASURE ABBREVIATIONS USED IN THIS REPORT 


L/min 


liter per minute mm 


millimeter 


mg/m- 5 


milligram per cubic meter pet 


percent 


yg/m 3 


microgram per cubic meter yr 


year 



RESPIRABLE DUST LEVELS IN COAL, METAL, AND NONMETAL MINES 



By W. F. Watts, Jr., 1 and D. R. Parker 2 



ABSTRACT 

In 1980 the Bureau of Mines developed the Mine Inspection Data Analy- 
sis System (MIDAS). MIDAS is a computerized, industrial hygiene data 
base capable of statistically analyzing environmental data collected in 
coal and noncoal mines and mills by Mine Safety and Health Administra- 
tion (MSHA) inspectors or mine operators. The objectives of this report 
are to describe the current contents of MIDAS, to report analyses of 
coal and noncoal mine respirable dust samples collected by MSHA inspec- 
tors and to evaluate the proposed change in the metal and nonmetal 
respirable dust standard from a formula based upon the percentage of 
quartz identified in the sample to 100 ug/m 3 of respirable quartz. 

Based on samples collected by MSHA inspectors, changing the noncoal 
respirable dust standard would result in 4 pet fewer samples with dust 
concentrations exceeding the standard. Analysis of respirable coal dust 
data collected by MSHA inspectors showed that mines with longwall plows 
or shears had the highest geometric mean concentrations (1.64 and 1.29 
mg/ra 3 , respectively). Mine operations using continuous rippers out- 
numbered longwall mine operations about 10 to 1 and had a geometric mean 
concentration of 0.66 mg/m 3 . 

industrial hygienist, Twin Cities Research Center, Bureau of Mines, Minneapolis, 
MN. 

2 Mine safety and health specialist, Mine Safety and Health Administration, U.S. 
Department of Labor, Arlington, VA. 



INTRODUCTION 



In 1980 the National Academy of Sci- 
ences stated that because of insufficient 
respirable dust measurements and the pau- 
city of reliable information on the inci- 
dence of silicosis, the most critical 
research need in noncoal mining was a 
definition of the extent of the health 
problem associated with silica exposures 
in noncoal miners. It was further stated 
that the adequacy of the current standard 
could not be evaluated when the magnitude 
of exposures remains unknown (1_).3 

The Bureau of Mines responded to this 
report by establishing the Mine Inspec- 
tion Data Analysis System (MIDAS) as a 
part of the respirable dust research 
program. MIDAS is a computerized, indus- 
trial hygiene data base developed by 
the Bureau with the assistance of the 
Mine Safety and Health Administration 
(MSHA). It is available, on-line, via 
the Bureau's telecommunications network 
to Bureau, MSHA, and National Institute 
of Occupational Safety and Health (NIOSH) 
personnel involved in mining research. 
Since its inception, MIDAS has provided 
information on the magnitude of res- 
pirable dust levels in noncoal mines, 
which is used to prioritize problems, 
determine trends in exposure, and to 
evaluate standards. In 1980 MIDAS con- 
tained only environmental industrial 
hygiene data collected from metal and 



nonmetal mines and mills by MSHA inspec- 
tors. These samples are collected to 
determine whether or not the mine or 
mill is in compliance with MSHA air qual- 
ity regulations. 

The first expansion of MIDAS took place 
in 1982 when data from a scientific 
survey of 22 mines were added to the 
data base. The survey was conducted 
from 1976 through 1978 in metal and 
nonmetal mines by MSHA personnel. The 
most recent expansion of MIDAS occurred 
in 1985 when coal mine respirable dust 
data were added to the data base. Unlike 
the noncoal data, the great majority 
of these samples were collected by coal 
mine operators, as opposed to MSHA in- 
spectors. MSHA updates the metal-non- 
metal and coal mine compliance data on a 
yearly basis. 

The objectives of this report are to 
describe the current contents of MIDAS, 
to report analyses of coal and noncoal 
mine respirable dust samples collected by 
MSHA inspectors, and to evaluate the pro- 
posed change in the metal and non- 
metal respirable dust standard. The 
report is divided into three major sec- 
tions: A description of the MIDAS metal 
and nonmetal subsystem, a description of 
the MIDAS coal subsystem, and a discus- 
sion of results from recent analyses of 
these data. 



MIDAS METAL AND NONMETAL SUBSYSTEM 



REGULATORY REQUIREMENTS 

MSHA regulates health and safety con- 
ditions and practices in metal and non- 
metal mines and mills under the authority 
of the Federal Mine Safety and Health Act 
of 1977, as amended (2.)* The specific 
regulations are found in the Code of 
Federal Regulations, Title 30 (3). Stan- 
dards in these regulations for airborne 
contaminants and physical agents were 
adopted from the 1973 recommended 

n •■■■■■■■■ ' — 

J Underlmed numbers in parentheses re- 
fer to items in the list of references 
preceding the appendix at the end of this 
report. 



threshold limit values (TLV's) of the 
American Conference of Governmental In- 
dustrial Hygienists (ACGIH) (4_). Compli- 
ance with these regulations is determined 
by the collection of environmental sam- 
ples by MSHA inspectors. 

DATA DESCRIPTION 

Since 1974 over 415,000 environmental 
samples have been collected by MSHA and 
records of these samples are edited and 
stored in MIDAS. Details of the editing 
procedure have been previously reported 
(_5). MSHA has collected samples for 132 
different contaminants, but samples for 
10 contaminants account for 91 pet of the 



415,000 records. These contaminants are 
listed in table 1. 

Data from metal and nonmetal sampling 
are of two types: personal (which are 
either partial- or full-shift samples 
collected on individuals) and area (which 
are short-term "grab" samples collected 
in the mine environment) . Each sample 
record contains at a minimum the mine 
identification number, date, contaminant 
code, contaminant concentration, and 
standard industrial classification (SIC) 
code. In addition, the personal samples 
contain codes to describe the worker's 
occupation, and location. In 1983 MSHA 
expanded the number of codes used to 
describe occupation, location, and -com- 
modity. These changes were incorporated 
into the data base in 1984 by convert- 
ing the pre-1983 codes to the new codes 
adopted by MSHA. The new codes for 
occupation, location, and commodity are 
listed in appendix tables A-l through 
A-3. 

An additional 15,000 samples were 
collected during a survey of 22 metal 
and nonmetal underground mines. MSHA 
conducted the survey in order to 
determine exposures to quartz-bearing 
dusts and to exhaust emissions produced 
by diesel engines used underground. 



The 22-mine-survey data are the only 
data stored in MIDAS that were not 
collected to determine compliance with 
regulatory standards. 

Environmental data from the 22-mine- 
survey include full-shift, personal sam- 
ples and short-term grab samples. Full- 
shift samples were used to measure 
concentrations of nitrogen dioxide, 
respirable dust, and total dust. The 
same miners were sampled for both dust 
and nitrogen dioxide. Grab samples were 
analyzed for a wide array of gases in- 
cluding carbon monoxide, carbon dioxide, 
and trace substances. Details of the 
survey and the major findings have been 
reported elsewhere (_6-7) . 

The data base also contains an index of 
all metal and nonmetal mine properties 
in the United States. Each property is 
listed with a unique mine identifica- 
tion number, its location, the property 
name, company name, approximate number of 
employees, year-round or other status, 
mine type, and standard industrial clas- 
sification code (SIC). Pertinent infor- 
mation from this file is added to the 
records of environmental samples to 
assist in grouping similar records for 
analysis. The index is updated annually 
by MSHA. 



TABLE 1. - Contaminants most frequently 
sampled in metal and nonmetal mines 



Contaminant 



Noise 

Respirable dust with 
>1 pet quartz 

Carbon monoxide 

Methane , 

Radon daughters 

Carbon dioxide 

Total dust 

Oxygen , 

Respirable dust with 
<1 pet quartz , 

Nitrogen dioxide...., 
Subtotal , 

Others 

Total 



Sample 



Type Number 



FS 

FS 
ST 
ST 
ST 
ST 
FS 
ST 

FS 
ST 



NAp 
NAp 



NAp 



112,126 

50,508 
39,830 
36,412 
34,910 
30,767 
26,637 
21,251 

14,706 
12,293 



379,440 
35,740 



415,180 



Pet of 
total 



27.0 

12.2 
9.6 
8.8 
8.4 
7.4 
3.2 
5.1 

3.5 
3.0 



91.4 
8.6 



100.0 



FS Full-shift personal exposure sample. 
NAp Not applicable. 
ST Short-term sample. 



SOFTWARE 

Data base software has undergone sev- 
eral phases of development since 1980. 
Each phase has resulted in the develop- 
ment of more comprehensive and user- 
friendly computer programs. Currently, 
software is accessed through one program 
that asks several questions, which re- 
sults in the introduction of a sequence 
of submenus. The submenus list the 
available programs for the type of data 
being analyzed and ask the user to select 
the desired program. Once a program is 
selected, a description of the program 
is displayed and the user is asked to 
specify detailed information. This in- 
formation includes program options, file 
names, code groups, and sort order. The 
results may be immediately retrieved upon 
completion of data processing, or in 
cases where large volumes of data are 
being processed the user may submit a job 



for overnight processing. This reduces 
computing costs and ensures adequate 
process time. Results can be retrieved 
the following day. 

The software for the metal and nonmetal 
subsystem was designed to accomplish the 
following tasks: record selection, file 
creation, record sorting, data analysis, 
and reporting of results. Records can be 
selected based upon user-specified varia- 
bles from the original master files or 
from previously created user files, and 
stored in a new data file. Sorting of 
records in a preset order is required for 
the use of certain programs, to ensure 
the efficient use of computer process 
time. Sorting requirements are noted in 
the program descriptions found at the 



beginning of each program. Analysis is 
accomplished using a variety of descrip- 
tive statistics such as the geometric 
mean (GM), the geometric standard devia- 
tion (GSD), and the percentage of samples 
greater than the threshold limit value 
(>TLV, pet). Graphic aids such as cumu- 
lative frequency plots are also availa- 
ble. Results are reported in the form of 
tables or graphs. 

In addition to software designed spe- 
cifically for MIDAS, the user may select 
other statistical software from the soft- 
ware library maintained by the Bureau. 
These programs are capable of calculating 
a wide array of descriptive and infer- 
ential statistics (8). 



MIDAS COAL SUBSYSTEM 



REGULATORY REQUIREMENTS 

In 1970 a mandatory respirable dust 
standard of 3.0 mg/m 3 was established for 
underground coal mines under the Federal 
Coal Mine Health and Safety Act of 1969. 
This standard was subsequently lowered in 
1972 to 2.0 mg/ra . Mandatory dust stan- 
dards for surface work areas of under- 
ground coal mines and surface mines also 
became effective in 1972. These regula- 
tions were continued under the Federal 
Mine Safety and Health Act of 1977 (_9) , 
which amended the 1969 coal act and 
merged coal and noncoal regulations into 
one law. In the 1969 act, "concentration 
of respirable dust" was defined as a 
measurement made with a Mining Research 
Establishment (MRE, Casella 113A) instru- 
ment or such equivalent concentration 
measured with another device. The 1977 
act changed the definition of "concen- 
tration of respirable dust" to be the 
"average concentration of respirable dust 
measured with a device approved by the 
Secretary and the Secretary of HEW." The 
device approved for measuring respirable 
dust uses a Dorr-Oliver 10-mm nylon 
cyclone to remove the nonrespirable frac- 
tion of dust sampled. Measurements made 
with this device are converted to equiva- 
lent MRE concentrations by multiplying by 
a constant factor of 1.38 ( 1_0 ) . Specific 
regulations detailing the collection of 



respirable dust samples by mine operators 
are found in the Code of Federal Regula- 
tions, Title 30 (3). Since 1970, more 
than 6 million respirable dust samples 
have been collected by coal mine opera- 
tors and MSHA inspectors to determine 
compliance with the 2.0-mg/m 3 standard. 

DATA DESCRIPTION 

In 1985 the Bureau received the respi- 
rable coal dust data from MSHA. Because 
of the large volume of data, only the 
1981 through 1985 records of samples col- 
lected by MSHA inspectors, and the 1985 
operator samples, are available in the 
data base. However records dating as 
far back as 1970 are stored on tape and 
can be loaded into the data base upon 
request. 

The MSHA coal dust records had three 
record formats: one corresponding to 
samples collected from 1970 to 1980, 
one corresponding to samples collected 
from 1980 to 1984 by operators, and one 
corresponding to samples collected from 
1980 to 1984 by inspectors. However, in 
order to conserve disk storage space and 
to simplify software development and 
analysis, the coal dust records were 
revised to reflect only one record type. 
Information that was not required for 
analysis was eliminated. Information 
that was retained but was not consistent 



between the different record types caused 
the creation of blank fields in some 
records. Records containing erroneous 
codes were removed by editing. 

Retained information that was recorded 
in the same manner on all records in- 
cludes State, mine identification number, 
sample date, dust concentration, tons 
of coal produced, and occupation code. 
Information that appears on all records 
but with different codes includes mine 
type, sample type, and mining method. 
Other information appearing on the rec- 
ords includes mine section or mechanized 
mining unit number, ventilation code, and 
the MSHA field office code. Table A-4 
lists the most frequently used occupation 
codes, and tables A- 5 through A- 7 list 
the codes used to describe mine type, 
sample type, and mining method. In addi- 
tion to the information listed above, 
every record contains a numerical code 



that allows rapid sorting into one of 
four groups: 1970-80 inspector sample, 
1970-80 operator sample, 1980-84 inspec- 
tor sample, and 1980-84 operator sample. 

SOFTWARE 

Software is currently being developed 
to analyze the coal dust data, and wher- 
ever possible, software developed for the 
metal and nonmetal subsystem is being 
modified for use with the coal subsystem. 
Examples of software under development 
include trends programs to compute sta- 
tistics for years, groups of years, and 
occupations; table programs to compute 
statistics for data grouped by occupa- 
tion, mining methods, and sample types; 
and graphics programs to produce plots by 
occupation, mining method, and sample 
type. 



RESPIRABLE DUST ANALYSIS 



METAL AND NONMETAL 

Since 1974 MSHA inspectors have col- 
lected more than 50,000 gravimetric sam- 
ples for dust containing respirable 
quartz (RQ) . The RQ sample is collected 
on a filter after the aerosol has passed 
through a cyclone preclassif ier at a flow 
rate of 1.7 L/min. The TLV for RQ is de- 
termined by collecting a respirable dust 
sample, analyzing for quartz content, ^ 
and calculating the TLV by dividing per- 
cent RQ plus 2 into 10 when the quartz 
content (percent RQ) is >1 pet ( 4_) . The 
resultant TLV is expressed in milligrams 
per cubic meter. The TLV for RQ is in- 
versely proportional to the quartz con- 
tent of the sample. Thus, for a given 
exposure level the magnitude of the toxi- 
city is proportional to the quartz con- 
tent (11). The factor 2 in the TLV 
formula ensures that dust exposures will 
not be excessively high when the quartz 
content is less than 5 pet and effec- 
tively limits the dust concentration to 
5 mg/m when no quartz is identified in 
the sample. 

4 puartz content is determined by X-ray 
diffraction after the filter has been 
weighed. 



In 1983 MSHA proposed to revise many of 
the existing health regulations (12) . 
Included in these revisions was a pro- 
posed change in the RQ standard. The 
proposed new standard, which is still 
undergoing review, is 100 yg/m 3 of respi- 
rable quartz. The effects of changing 
the RQ standard on compliance deter- 
minations are discussed in a subsequent 
section. 

The yearly statistics for RQ are shown 
in table 2. Data shown in table 2 must 
be interpreted in the context of MSHA 
policy and regulatory changes that may 
have altered sampling strategies. These 
changes have been discussed in depth 
elsewhere ( 13 ) , but warrant a brief 
review. 

MSHA inspectors collect dust samples 
in order to determine compliance. This 
is accomplished by sampling workers 
thought to have the greatest risk of 
overexposure, and a sample exceeding the 
standard by 20 pet is considered out of 
compliance. 

The sampling strategy used in metal and 
nonmetal mines and mills tends to be 
judgmental in that it is not based on a 

probability model assuming randomness. 
This creates a statistical problem: These 



TABLE 2. - Yearly statistics for RQ 



Year 



Samples 



>TLV, 
pet 



Concentration, mg/nr 



GM 



Median 



GSD 



GM 
C-TLV 



1974 , 

1975 , 

1976 , 

1977 , 

1978 

1979 , 

1980 

1981 , 

1982 , 

1983 , 

1984 

Total or 
average. 



284 
2,648 
6,223 
7,566 
7,840 
7,780 
4,744 
4,423 
1,640 
3,399 
3,961 



50,508 



44.37 
27.95 
25.16 
18.90 
15.46 
13.62 
14.69 
16.69 
17.26 
17.01 
17.22 



0.58 
.49 
.51 
.44 
.40 
.37 
.40 
.43 
.46 
.45 
.45 



0.54 
.47 
.48 
.43 
.38 
.34 
.37 
.40 
.43 
.41 
.40 



2.62 
2.94 
3.08 
2.96 
3.00 
2.98 
2.63 
2.58 
2.72 
2.35 
2.43 



18.04 



.43 



.40 



2.84 



0.86 
.53 
.45 
.37 
.34 
.31 
.33 
.36 
.39 
.40 
.39 



.37 



GM Geometric mean. 

GM C-TLV Geometric mean concentration-to-TLV ratio. 

GSD Geometric standard deviation. 

TLV Threshold limit value. 



data may not be representative of all ex- 
posures, so the classical assumptions of 
randomness, homoscedasticity (homogeneous 
variance) , and normal distribution may 
not apply. In addition, anything that 
affects the number of samples collected 
is important because it alters the sampl- 
ing strategy. Two examples of such al- 
terations are the Federal Mine Safety and 
Health Act of 1977 ( 2^ , and the tempo- 
rary removal of stone, sand and gravel, 
and other commodities from MSHA's juris- 
diction for most of fiscal year 1982. 

The passage of the 1977 act was fol- 
lowed by an increase in the number of RQ 
samples collected over previous years 
until 1980 when internal MSHA policy 
changes caused a marked reduction in the 
number of RQ samples. This was followed 
in 1982 with the temporary loss of juris- 
diction over stone, sand and gravel, and 
other commodities accompanied by a sharp 
decrease in the number of RQ samples as 
shown in table 2. With the restoration 
of MSHA's jurisdiction over stone, sand 
and gravel, and other commodities in the 
1983-84 period, the number of samples 
reported rebounded close to the level in 
1980. Overall, the data in table 2 show 
that for the more than 50,000 RQ 
samples over the 1974-84 period, more 
than 18 pet ("9,000) of the samples 
exceeded the TLV. 



Exposures by Mine Type and Occupation 

Table 3 shows RQ exposures by mine type 
for two time periods, 1974-79 and 1980- 
84. The location groups, underground, 
surface, and mill, are defined in table 
A-2, and the commodity groups, stone, 
metal, nonmetal, and sand and gravel, are 
defined in table A-3. For each group 
the table shows the number of samples, 
geometric mean concentration (GM CONC) , 
geometric mean concentration-TLV ratio 
(GM C-TLV), percentage of samples exceed- 
ing the TLV, and the percentage of 
workers wearing respirators at the time 
the sample was collected. 

Several mine types have shown substan- 
tial improvement from the 1974-79 to 
1980-84 sample period. Nonmetal mills 
have reduced the percentage of samples 
exceeding the TLV from 40.1 pet to 23.9 
pet, while increasing the percentage of 
workers wearing respirators from 49.9 pet 
to 64.9 pet. The GM CONC was reduced 
from 0.84 to 0.66 mg/m 3 . Overexposures 
were also sharply reduced at industrial 
sand mills (32.9 to 22.1 pet), while 
workers wearing respiratory protection 
increased 13.7 pet. At both nonmetal 
mills and industrial sand mills, the 
product is typically a crushed or ground 
silica sand with a very high quartz 
content. 



TABLE 3. - RQ exposures by mine type for 1974-79 and 1980-84 



Commodity group 



Metal: 

Samples 

GM CONC mg/m 3 .. 

GM C-TLV 

>TLV pet.. 

PROT pet. . 

Nonmetal: 

Samples 

GM CONC mg/m 3 .. 

GM C-TLV 

>TLV pet. . 

PROT pet. . 

Sand and gravel: 

Samples 

GM CONC mg/m 3 . . 

GM C-TLV 

>TLV pet.. 

PROT pet.. 

Stone: 

Samples 

GM CONC rag/m 3 .. 

GM C-TLV 

>TLV pet. . 

PROT pet.. 

Total: ' 

Samples 

GM CONC mg/m 3 .. 

GM C-TLV 

>TLV pet. . 

PROT pet.. 



1974-79 



UG 
mine 



2,815 
0.57 
0.46 
18.3 
39.5 

608 
0.74 
0.52 
26.8 
32.9 

NAp 
NAp 
NAp 
NAp 
NAp 

562 
0.86 
0.44 
19.4 
34.9 

3,985 
0.63 
0.47 
19.8 
37.9 



Surface 
mine 



1,604 
0.30 
0.28 
11.2 
25.9 

1,820 
0.43 
0.39 
18.7 
39.4 

4,192 
0.24 
0.28 
12.8 
22.6 

11,347 
0.37 
0.29 
13.4 
23.4 

18,963 
0.34 
0.30 
13.6 
25.0 



Mill Total 



1,892 
0.46 
0.47 
24.3 
35.6 

2,252 
0.84 
0.78 
40.1 
49.9 

799 
0.37 
0.60 
32.9 
46.3 

4,385 
0.58 
0.49 
25.7 
42.9 

9,328 
0.58 
0.55 
29.5 
43.4 



6,311 
0.45 
0.41 
18.3 
34.9 

4,680 
0.64 
0.57 
30.1 
43.6 

4,991 
0.26 
0.32 
16.0 
26.4 

16,294 
0.43 
0.34 
16.9 
29.1 

32,276 
0.43 
0.37 
19.0 
31.9 



1980-84 



UG 
mine 



1,548 
0.55 
0.42 
17.0 
58.3 

260 
0.58 
0.43 
18.5 
58.5 

NAp 
NAp 
NAp 
NAp 
NAp 

484 
0.70 
0.34 
14.0 
32.2 

2,292 
0.58 
0.40 
16.6 
52.8 



Surface 
mine 



1,093 
0.31 
0.29 
11.7 
45.2 

612 
0.38 
0.29 
18.7 
47.9 

1,905 
0.35 
0.37 
14.5 
36.6 

5,330 
0.39 
0.29 
11.9 
35.5 

8,940 
0.37 
0.31 
12.6 
37.8 



Mill 



1,080 
0.37 
0.35 
15.9 
50.0 

1,425 
0.66 
0.53 
23.9 
64.9 

1,413 
0.38 
0.50 
22.1 
59.0 

3,014 
0.49 
0.43 
21.5 
51.0 

6,932 
0.47 
0.45 
21.3 
55.3 



Total 



3,721 
0.41 
0.36 
15.2 
52.1 

2,297 
0.56 
0.44 
20.6 
59.6 

3,318 
0.36 
0.42 
17.8 
46.1 

8,828 
0.43 
0.34 
15.3 
40.6 

18,164 
0.43 
0.37 
16.4 

46.4 



GM CONC Geometric mean concentration. 

GM C-TLV Geometric mean concentration-to-TLV ratio. 

NAp Not applicable. 

PROT Respiratory protection. 

TLV Threshold limit value. 

UG Underground. 



68 records are excluded because no SIC code was reported. 



Overall the table shows that the use of 
respiratory protection is increasing and 
that dust levels are decreasing. Seven 
of the eleven mine types show reduced 
GM CONC while only four (surface stone 
quarries, metal mines, sand and gravel 
mills, and surface quarries) show 
slightly higher GM CONC. Sand and gravel 
quarries had a small increase in the per- 
cent of samples exceeding the TLV despite 
a large drop in the number of samples 
collected. 



Table 4 shows the changes in the per- 
centage of samples exceeding the TLV and 
the GM CONC for 17 frequently sampled 
occupations for the same time periods, 
1974-79 and 1980-84. Nearly 90 pet of 
the over 50,000 RQ samples are accounted 
for in the table, and each occupation 
has a minimum of 200 samples in each time 
period. The bagging, flotation, jack 
stoper drill, and trucker occupations had 
10 pet fewer samples exceeding the TLV. 
Stope miner, motorman, and laborer and 



TABLE 4. - RQ exposures by metal and nonmetal occupation 1 for 1974-79 and 1980-84 



Occupation 



1974-79 



Samples 



>TLV, 
pet 



GM CONC, 
mg/m 3 



1980-84 



Samples 



>TLV, 
pet 



GM CONC, 
mg/m 3 



Change 
>TLV, 
pet 



Bagging and packing 

Flotation 

Jack stoper drill 

Trucker 

Ball and rod mill 

Cleanup man 

Sizing and washing 

Mechanic 

Crusher 

Dryer and kiln 

Pneumatic drill 

Bulldozer 

Wagon drill 

Front-end loader 

Stope miner 

Motorman 

Laborer and bullgang. . . . 
Total or average. . . 



1,384 

422 

470 

409 

1,178 

3,344 

1,239 

1,318 

4,894 

1,220 

703 

792 

1,030 

9,254 

964 

743 

350 



44.0 
19.0 
25.5 
14.2 
31.4 
28.3 
23.3 
14.5 
23.5 
24.1 
23.2 
12.9 
23.8 
7.6 
13.0 
12.5 
18.0 



0.73 
.43 
.84 
.37 
.62 
.54 
.41 
.42 
.51 
.46 
.55 
.30 
.50 
.29 
.47 
.33 
.54 



1,360 
232 
201 
850 
341 

1,354 
510 
372 

3,434 
761 
344 
328 
331 

4,195 
284 
344 
221 



33.1 

8.2 
14.9 

4.2 
21.7 
21.2 
17.5 

8.9 
20.0 
22.7 
22.1 
11.9 
23.0 

6.9 
13.4 
13.1 
19.9 



0.59 
.33 
.67 
.33 
.43 
.49 
.39 
.39 
.48 
.46 
.53 
.32 
.49 
.34 
.51 
.34 
.49 



-10.9 

-10.8 

-10.6 

-10.0 

-9.7 

-7.1 

-5.8 

-5.6 

-3.5 

-1.4 

-1.1 

-1.0 

-.8 

-.7 

.4 

.6 

1.9 



29,714 



21.1 



.49 



15,462 



16.6 



.45 



-4.5 



GM CONC 



Geometric mean 
Threshold limit 



TLV 
See table A-l for corapl 



concentrati 

value, 
ete listing 



on. 



of codes, occupations, and samples. 



NOTE. — Selected occupations had at least 200 samples in each period. 



bullgang occupations show slight in- 
creases (less than 2 pet) in the percent- 
age of samples exceeding the TLV. The 
average reduction in the percentage of 
samples exceeding the TLV was 4.5 pet 
for the occupations shown in the table. 
Dramatic changes in the percentage of 
sampled workers wearing respiratory pro- 
tection for these occupations are illus- 
trated in table A-8. All 17 occupations 
experienced an increase in the use of 
respiratory protection ranging from 5 to 
20 pet despite reduction in dust levels. 
The average respirator wear increase for 
the occupations was 14 pet. The increase 
in the use of respiratory protection is 
attributed to increased worker awareness 
of health problems associated with respi- 
rable dust containing quartz and MSHA's 
respiratory protection program. 

Effect of Changing the RQ Standard 

As previously mentioned, MSHA has pro- 
posed to change the TLV for RQ from 
the formula to 100 Ug/m 3 of respirable 



quartz. MIDAS can be used to evaluate 
the effect of this change because every 
respirable dust record has the time- 
weighted average dust concentration and 
the percentage of quartz, thus the time- 
weighted average quartz concentration can 
be calculated for each record and com- 
pared to the proposed standard. Table 5 
summarizes the quartz statistics for sel- 
ected commodities. These commodities ac- 
count for 46,846 of the 50,400 (92.7 pet) 
of the samples summarized in table 3. 

A previous paper (13) showed that both 
respirable dust and quartz concentrations 
approximated log-normal distributions. 
When a distribution is log-normal, the 
geometric mean or median and geometric 
standard deviation are the best measures 
of central tendency and dispersion. In 
table 5 both the arithmetic and geometric 
parameters are shown to facilitate com- 
parisons with other sets of data where 
only the arithmetic mean (AM) and arith- 
metic standard deviation were computed. 
The GM CONC's are all well below 
the proposed standard, whereas six 



TABLE 5. - Quartz statistics for selected commodities 1 



Commodity 



Samples 



Concentration, yg/m 3 



AM ASD GM GSD 



Quartz, pet 
(AM) 



Metal: 

Copper 

Gold 

Iron 

Lead and zinc 

Molybdenum 

Silver 

Uranium 

Nonmetal: 

Common clay 

Fire clay 

Nonmetal, not elsewhere classified. 

Phosphate rock 

Sand and gravel 

Stone: 

Cement 

Granite: 

Crushed • 

Dimension 

Limestone: Crushed 

Sandstone: 

Crushed 

Dimension • 

Stone: Crushed 

Traprock : Crushed 



2,240 
1,150 
2,593 
1,044 
600 
756 
1,158 

2,792 
784 
881 
531 

8,309 

1,232 

3,206 

1,113 

13,054 

3,421 
434 
689 
869 



84 
93 
49 
74 
101 
68 
50 

94 
98 
209 
58 
75 

35 

68 

102 

34 

140 

191 

120 

44 



254 
262 
121 
270 
193 
137 
181 

225 
199 
563 
106 
284 

68 

238 
195 
121 

294 

690 

339 

76 



30 
37 
21 
28 
50 
32 
22 

40 
45 
55 
29 
27 

16 

30 
46 
15 

52 
44 
40 
21 



8.6 
10.0 
9.5 
8.3 
9.1 
9.2 
7.5 

7.7 
8.4 

20.7 
9.1 

13.1 

4.0 

11.4 

11.4 

4.6 

22.9 

21.7 

16.1 

6.8 



AM Arithmetic mean. 

ASD Arithmetic standard deviation. 

GM Geometric mean. 

GSD Geometric standard deviation. 

'See table A-3 for complete listing of 



SIC codes, commodities, and samples. 



commodities have AM CONC's exceeding 
the proposed standard of 100 yg/m 3 of 
respirable quartz. 

It would be expected that fewer samples 
would exceed the new standard. For exam- 
ple, if a worker is sampled during a 
work -shift and a mass of 0.82 mg of 
respirable dust is deposited on the 
filter, then the time-weighted average 
concentration of dust for that sample is 
1.0 mg/ra 3 . If the sample contains 9 pet 
quartz, the allowable respirable dust 
level is 0.91 mg/m 3 under the current 
standard. The time-weighted average res- 
pirable quartz concentration is 0.090 
mg/m 3 . This sample exceeds the current 
standard but not the proposed standard 
of 100 yg/m 3 (0.100 mg/m 3 ) of respirable 
quartz. Table 6 shows the percentage 



of samples exceeding both standards for 
the commodities listed in table 5. The 
proposed standard would result in the 
reporting of about 4 pet fewer samples 
exceeding the TLV, and no mining 
activity would be adversely affected. 

COAL 

The objective of respirable dust sam- 
pling in coal mines is to ensure compli- 
ance with the 2.0-mg/m 3 coal mine dust 
standard or with the more rigorous stan- 
dard if the mine dust aerosol contains 
more than 5 pet quartz. A mine is out of 
compliance if the arithmetic average of 
five samples is over the standard. MSHA 
inspectors and coal mine operators regu- 
larly sample miners or areas known to 



10 



TABLE 6. - Effect of changing the RQ TLV 



Commodity 1 



Samples 



>TLV, 
pet 



100 yg/m 3 ; 
pet 



Change, 
pet 



Metal: 

Copper 

Gold 

Iron 

Lead and zinc 

Molybdenum 

Silver 

Uranium 

Nonmetal: 

Common clay 

Fire clay 

Nonmetal, not elsewhere classified 

Phosphate rock 

Sand and gravel 

Stone: 

Cement 

Granite: 

Crushed 

Dimension 

Limestone: Crushed 

Sandstone: 

Crushed 

Dimension 

Stone: Crushed 

Traprock: Crushed 

All commodities: 2 

Total or average 

TLV Threshold limit value. 

1 See table A-3 for complete listing of SIC code 
Includes data for commodities not shown in the 



2,240 
1,150 
2,593 
1,044 
600 
756 
1,158 

2,792 

784 

881 

531 

8,309 

1,232 



19.1 
22.7 
12.1 
16.6 
32.2 
18.9 
11.3 

29.3 
31.9 
40.1 
15.6 
16.7 

13.0 



3,206 


16.9 


1,113 


30.0 


13,054 


9.9 


3,421 


34.1 


434 


30.6 


689 


27.6 


869 


13.1 



50,440 18.0 



15.0 
18.4 

9.6 
12.6 
26.0 
13.5 

7.9 

21.7 
23.8 
37.3 
11.5 
14.2 

7.6 

13.8 

25.0 

5.8 

31.8 

29.3 

25.0 

9.2 

14.1 



-4.0 
-4.3 
-2.5 
-4.6 
-6.2 
-5.4 
-3.4 

-7.6 
-7.8 
-2.8 
-4.1 
-2.5 

-5.4 

-3.1 
-5.0 
-4.1 

-2.3 
-1.3 
-2.6 
-3.9 

-3.9 



s, commodities, and samples, 
table. 



have high dust exposure. In underground 
mines, MSHA inspectors are required to 
sample specific occupations referred to 
as designated occupations (DO). A DO is 
an occupation on a mining operation that 
is typically exposed to the highest res- 
pirable dust concentration. Examples of 
DO's would include the longwall shearer 
operator or the continuous miner opera- 
tor. In addition, the MSHA inspectors 
sample other underground occupations sus- 
pected to have high dust exposures such 
as roof bolters. These occupations are 
referred to as nondesignated occupations 
(NDO's). 

The results from the respirable coal 
dust analysis reported below are re- 
stricted to samples collected only by 
MSHA inspectors from 1981-84, and are for 
the most part restricted to DO and NDO 



samples collected in underground mines. 
Results reported for surface coal mines 
are limited to specific occupations. 
Mine compliance data are not reported, 
but the percentage of samples exceeding 
the 2.0 mg/m 3 standard is reported. It 
should be emphasized that, in coal mines, 
a single sample that exceeds the standard 
does not automatically place the mine in 
a noncompliance status. 

MSHA is required to inspect all under- 
ground coal mines four times each year, 
collecting dust samples twice a year, 
but the population of mines inspected 
changes from year to year depending upon 
the market for coal and other factors. 
From 1981 through 1984, MSHA inspectors 
collected about 66,000 full-shift, per- 
sonal, respirable dust samples in under- 
ground coal mines. About 16,500 samples 



_^^^>^^^M^^M 



^H^M^H 



1 1 



were collected at approximately 1,550 
different underground mines per year. An 
additional 10,000 samples per year were 
collected at surface coal mines. 

Table 7 shows the yearly trends in 
exposure for underground DO and NDO sam- 
ples. The sample size, the mean dust 
concentration, and the percentage of sam- 
ples exceeding the 2.0-mg/m 3 standard 
remained relatively constant from 1981 
through 1984. Between 10 and 12 pet of 
the samples exceeded the standard and 
the GM CONC fluctuated between 0.59 and 
0.69 mg/m 3 . A coal mine is out of 
compliance only when an average of five 



samples exceeds the 2.0 mg/m 5 standard, 
thus there are far fewer mines out of 
compliance than there are samples exceed- 
ing the standard. On average, about 
1,800 samples exceeded the standard each 
year. 

Table 8 shows the 1984 statistics for 
DO and NDO underground mine samples 
grouped by mining method. The table 
accounts for more than 98 pet of all 
underground mine samples, despite the 
fact that methods of mining with less 
than 50 samples are not included because 
of small sample size. Mines with long- 
wall plows or shears have the highest GM 



TABLE 7. - Yearly trends in respirable dust exposure for 
samples collected in underground coal mines 



Statistic 



1981 



1982 



1983 



1984 



Samples 

>TLV pet. . 

Concentration, mg/m : 

AM 

ASD 

GM 

GSD 

Median 



16,233 
11.9 

1.12 
1.88 
0.66 
2.80 
0.80 



16,244 
11.0 

1.12 
1.86 
0.69 
2.68 

0.80 



16,687 
9.9 

1.01 
1.40 
0.59 
2.85 
0.70 



16,452 
11.9 

1.12 
1.97 
0.65 
2.83 
0.70 



AM Arithmetic mean. 

ASD Arithmetic standard deviation. 

GM Geometric mean. 

GSD Geometric standard deviation. 

TLV Threshold limit value. 



TABLE 8. - 1984 coal dust data by underground mining method 



Mining method 



Samples 



Concentration, mg/m 3 



GM 



GSD 



>TLV, 
pet 



Longwall plow 

Longwall shear 

Conventional cut machine 

Continuous ripper 

Continuous bore 

Continuous auger 

Scoop shoot solids 

Scoop cut machine 

Conventional shoot with loading machine 

Hand-load shoot solid 

GM Geometric mean. 

GSD Geometric standard deviation. 

TLV Threshold limit value. 

NOTE. — For inclusion in the table there had to be at least 50 samples and the min- 
ing methods are ranked by the GM concentration. 



151 

963 

1,558 

10,946 

153 

553 

525 

997 

84 

258 



1.64 
1.29 
.67 
.66 
.61 
.57 
.54 
.47 
.39 
.38 



2.25 
2.18 
2.69 
2.75 
3.02 
4.06 
3.18 
2.96 
2.70 
2.58 



43.7 

25.2 

10.2 

10.9 

10.5 

20.8 

9.3 

7.9 

7.1 

3.9 



12 



CONC (1.64 and 1.29 mg/m 3 , respectively) 
and the greatest percentage of samples 
exceeding the 2.0-mg/m 3 standard (43.7 
and 25.2 pet, respectively). However, 
many more samples (10,946) were recorded 
at mines using continuous rippers, where 
the GM CONC was 0.66 mg/m 3 and 10.9 pet 
of the samples exceeded the standard. 
Mines with augers had a lower GM CONC 
(0.57 mg/m 3 ) but 21 pet of the samples 
exceeded the standard. Augers also have 
the highest geometric standard deviation 
(4.06), which suggests that some of the 
reported dust concentrations are ex- 
tremely high. 

Table 9 is a cumulative frequency table 
that compares DO and NDO samples for the 
auger, continuous ripper, and longwall 
mining methods. Samples from longwall 
shears and plows were combined to in- 
crease the sample size. Four percentiles 
are shown— 20th, 50th, 80th, and 95th. A 
fifth value, the percentage of samples 
exceeding the 2.0-mg/m 3 standard (TLV) , 
is also shown. This can be converted to 
a percentile for each mining method by 
subtracting the value from 100. The per- 
centiles represent low exposure, median 
exposure, moderate exposure, and high 
exposure levels. For instance, at the 



95th percentile concentration 5 pet of 
the samples exceed that value. With one 
exception the DO percentile values are 
greater than or equal to the correspond- 
ing NDO values. The only exception is 
the 95th percentile longwall NDO value, 
which is 0.3 mg/m 3 higher than the DO 
values. This finding confirms MSHA's 
selection of DO's as those occupations 
with the highest overall exposures. The 
auger samples have the highest 95th per- 
centile values (7.8 and 6.0 rag/m 3 ) and 
the lowest 20th percentile values (0.1 
mg/m 3 ). This explains the high standard 
deviations for auger samples shown in 
table 8. Figure 1 illustrates the dis- 
tribution of these data, which is approx- 
imately log-normal and different for each 
mining method and sample type group. 

More mines use continuous rippers than 
any other mining method and these mines 
have the greatest number of samples 
exceeding the 2.0-mg/m 3 standard. Table 
10 shows that the average number of 
samples collected per year at mines using 
continuous rippers was 11,036 and that 
the average number of samples over the 
standard was 1,120 or 10.1 pet. During 
any single year between 1981 and 1984 
about 43 pet of the mines with continuous 



TABLE 9. - Differences between DO and NDO samples for three 
mining methods 



Group 



Samples 



Percentile concentrations, mg/ 



m 



20th 



50th 80th 95th 



>TLV, 
pet 



Auger: 

DO 

NDO 

Continuous ripper: 

DO 

NDO 

Longwall: 

DO 

NDO 



116 

437 

2,5 20 
8,426 

296 

818 



0.1 
0.1 

0.4 
0.2 

1.1 

0.7 



0.5 
0.5 

0.8 

0.7 

1.7 
1.4 



2.7 

1.8 

1.8 
1.5 

2.7 
2.2 



7.8 
6.0 

3.6 

2.7 

4.0 
4.3 



28.4 
18.8 

14.2 
9.9 

34.8 
25.2 



DO Designated occupation. 
NDO Nondesignated occupation. 
TLV Threshold limit value. 



i^MM 



95 



80 



50 



o 20 



UJ 
3 
O 
UJ 

tr 

U- 



15 



1 

A 


\ i r-" 


- 


/ KEY 




1 • DO 




O NDO 


V i d 


l i I 



0.7 



20 6- 



2.0 3.0 4.0 5.0 




95 



80 - 



50 - 



2.0 3.0 4.0 





1 1 ' 


i i \J 


? — • — 


c 










jS/S • 






Jl 


I 1 i 


KEY 

• DO 
O NDO 

l l 1 


i i i i 



20i 
0.1 

CONCENTRATION, mg/m 2 



0.5 



1.0 



2.0 3.0 5.0 7.0 10.0 



FIGURE 1.— Logarithmic probability plots of longwall {A), continuous ripper (8), and auger (C) samples grouped by designated 
occupation (DO) and nondesignated occupation (NDO). 



rippers had at least one sample exceeding 
the standard. For mines with longwall 
shears or plows, only 247 samples per 
year exceeded the standard at 40 differ- 
ent mines. Every mine reported to have a 
longwall operation also used continuous 
rippers for mine development. The dust 
concentrations were greater at mines with 
longwall operations but there were nearly 



nine times more continuous ripper opera- 
tions with one or more samples exceeding 
the 2.0-mg/m- 5 standard. However, as pre- 
viously mentioned this does not mean 
that all of these mines were out of 
compliance, because compliance with the 
standard is determined by an average of 
five samples. 



l<* 



TABLE 10. - Average number of samples exceeding 2.0 mg/m 3 for 1981-84 and 
average number of mines with samples exceeding 2.0-mg/m 3 standard 



Mining method 



Number 



Samples 



>TLV 



Number 



i£L 



Mines 



Number 



>TLV 



Number 



pet 



Continuous ripper . 

Conventional cut machine 

Scoop cut machine 

Longwall shear 

Continuous auger 

Scoop shoot solids 

Longwall plow . 

Conventional shoot with loading machine. 

Continuous bore • 

Hand-load shoot solid < 



11,036 

1,720 

1,027 

713 

530 

616 

130 

131 

91 

142 



1,120 

201 

76 

193 

95 

50 

54 

10 

7 

7 



10.1 

11.7 

7.4 

27.1 

17.9 

8.2 

41.5 

7.4 

7.7 

4.8 



808 

195 

151 

48 

70 

107 

9 

21 

13 

26 



350 

74 

36 

33 

29 

25 

7 

4 

3 

3 



43.2 
38.1 
24.1 
69.8 
41.6 
23.4 
80.6 
20.5 
21.6 
12.4 



TLV Threshold limit value. 

NOTE. — The mining methods are ranked by the number of mines with at least 1 sample 
over the TLV. 



Table 11 shows the 1984 coal mine dust 
data for the most frequently sampled 
underground and surface occupations. 
Four occupations, longwall shear or plow 
operator, return side auger jack setter, 
longwall jack setter, and surface fine 
coal plant operator, had more than 28 pet 
of the samples exceeding the 2.0-mg/m- 5 
standard for a total of 382 samples. 
In comparison, 558 samples collected on 
continuous miner operators (14.2 pet) and 
helpers (13.7 pet), and 420 (11.9 pet) 
samples collected on roof bolters were 
over the standard. As previously shown, 
mines with longwall operations have the 
highest GM CONC and longwall operators 
have the highest exposures. However, at 
the present time there are relatively few 
longwalls compared to other methods of 



mining so occupations not specific to 
longwall operation, such as roof bolters 
and continuous miner operators, account 
for more samples exceeding the 2.0-mg/m 3 
standard. 

Table 12 shows the yearly statistics 
for five dusty occupations: continuous 
miner helper, longwall jacksetter, long- 
wall shear-plow operator, and roof 
bolter. There was a reduction in the 
GM CONC and the percentage of samples 
exceeding the 2.0-mg/m 3 standard for the 
longwall shear-plow operator and a re- 
duction in the percentage of samples 
exceeding the standard for the longwall 
jack setter. Levels for the other three 
occupations remained essentially constant 
over the 1981-84 4-yr period. 



n^nm^HMi 



TABLE 11. - 1984 coal mine dust data for underground and surface occupations 



Occupation 



Samples 



Concentration, mg/m 



GM GSD 



AM ASD 



>TLV, 
pet 



Underground: 

Longwall tailgate side 

Longwall jack setter 

Headgate operator 

Auger jack setter, return side 

Continuous miner operator 

Loading machine operator 

Continuous miner helper 

Roof bolter 

Roof bolter helper 

Cutting machine operator 

Utility man 

Shotf irer < 

Auger jack setter, intake 

Section foreman 

Shuttle car operator 

Mobile bridge operator 

Shuttle car operator standard side. 

Coal drill operator 

Scoop car operator , 

Mechanic • 

Motorman , 

Hand loader. ' 

Surface: 

Fine coal plant operator 

Highwall drill operator 

Cleanup man. 

Scalper-screen operator 

Cleaning plant operator 

Laborer 

Refuse truck driver 

Tipple operator 

Mechanic 

Bulldozer operator 

Scraper operator 

Highlif t operator 

Oiler-greaser 

Coal truck driver 

Coal shovel operator 

Crane-dragline operator 



387 
499 
136 
116 

2,579 
283 

1,405 

3,451 
629 
516 
304 
174 
279 
277 
757 
136 

2,123 
483 
938 
181 
148 
117 

197 
817 
169 
108 
216 
525 
634 
375 
339 

1,651 
221 

1,565 
189 
179 
107 
232 



1.66 
1.50 
.87 
.83 
.77 
.76 
.73 
.69 
.65 
.64 
.64 
.58 
.57 
.55 
.54 
.53 
.51 
.48 
.47 
.44 
.41 
.30 

1.00 
.62 
.58 
.58 
.49 
.44 
.38 
.35 
.31 
.30 
.25 
.22 
.22 
.22 
.19 
.17 



1.93 
1.84 
2.55 
4.89 
2.83 
2.58 
2.76 
2.74 
2.80 
2.99 
2.68 
2.93 
3.81 
2.52 
2.59 
3.13 
2.58 
2.94 
2.85 
2.44 
3.01 
2.47 



.85 
.36 
.92 
.67 
.90 
.11 
.61 
.90 
.86 
.49 
.54 
.29 
.30 
.01 
.12 
.14 



2.03 

1.80 

1.30 

2.44 

1.31 

1.15 

1.15 

1.09 

1.02 

1.23 

1.17 

1.00 

1.69 

.83 

.86 

1.03 

.80 

.97 

.78 

.66 

.74 

.47 

1.51 
1.29 
1.04 
.88 
.88 
.97 
.59 
.64 
.63 
.48 
.43 
.34 
.32 
.29 
.26 
.43 



1.45 

1.30 

1.24 

4.17 

2.31 

1.30 

1.31 

1.24 

.97 

3.05 

4.20 

1.28 

5.47 

.99 

1.22 

1.45 

2.00 

3.02 

.99 

.81 

.96 

.50 

1.19 

2.05 

1.67 

.80 

1.50 

3.16 

.61 

.86 

2.19 

.98 

.69 

.43 

.35 

.24 

.28 

3.15 



34.6 

28.7 

18.4 

36.2 

14.2 

12.4 

13.7 

11.9 

12.1 

12.2 

9.1 

10.3 

16.8 

5.4 

4.9 

11.0 

5.6 

6.2 

5.6 

2.8 

6.1 

4.3 

32.0 

17.1 

10.0 

9.3 

6.5 

7.4 

3.3 

6.4 

2.9 

2.0 

3.2 

1.3 

.5 





.9 



AM Arithmetic mean. 
ASD Arithmetic standard deviation. 
GM Geometric mean. 
See table A-4 for complete list of 



GSD Geometric 
TLV Threshold 



standard 
limit va 



deviation, 
lue. 



codes, occupations, and samples 



NOTE. — Only occupations with at least 100 
they are ranked by GM concentration. 



samples are included in this table and 



16 



TABLE 12. - Trends in exposure for five underground coal mine occupations 



Occupation 

Continuous miner operator: 

Samples 

AM CONC mg/m 3 

ASD mg/m 3 , 

GM CONC rag/m 3 

GSD rag/m 3 

>TLV pet 

Continuous miner helper: 

Samples 

AM CONC mg/m 3 . 

ASD mg/m 3 

GM CONC mg/m 3 , 

GSD mg/m3, 

> TLV pet 

Longwall jack setter: 

Samples 

AM CONC rag/m 3 , 

ASD mg/m 3 

GM CONC rag/m 3 

GSD rag/m 3 , 

>TLV pet 

Longwall shear-plow operator: 

Samples 

AM CONC rag/m3 , 

ASD rag/m 3 

GM CONC mg/m 3 , 

GSD mg/m 3 , 

>TLV pet. 

Roof bolter: 

Samples 

AM CONC . rag/m 3 , 

ASD rag/ra 3 , 

GM CONC mg/m 3 . 

GSD mg/m 3 . 

>TLV pet, 

AM CONC Arithmetic mean concentration. 

ASD Arithmetic standard deviation. 

GM CONC Geometric mean concentration. 

GSD Geometric mean standard deviation. 

TLV Threshold limit value. 



1981 



1982 



1983 



1984 



2,196 
1.30 
2.20 
0.82 
2.63 
14.6 

1,349 
1.14 
1.16 
0.77 
2.61 
12.7 

269 
1.72 
1.30 
1.35 
2.10 
32.0 

188 
2.60 
2.49 
1.88 
2.30 
47.9 

3,382 

1.21 
2.01 
0.76 
2.70 
13.3 



2,484 
1.26 
2.45 
0.82 
2.52 
13.0 

1,512 
1.12 
1.06 
0.78 
2.45 
10.7 

296 

1.79 
1.39 
1.43 
2.00 
40.4 

213 
2.16 
1.53 
1.74 
1.97 
41.3 

3,464 
1.24 
2.43 
0.77 
2.67 
13.0 



2,445 
1.14 
1.21 
0.73 
2.70 
12.4 

1,413 
1.01 
1.10 
0.66 
2.67 
9.5 

414 
1.79 
1.65 
1.40 
2.00 
27.5 

328 
1.95 
1.35 
1.57 
1.97 
34.4 

3,624 
1.00 
1.18 
0.63 
2.75 
9.6 



2,579 
1.31 
2.31 
0.77 
2.83 
14.2 

1,405 
1.15 
1.31 
0.73 
2.76 
13.7 

499 
1.80 
1.30 
1.50 
1.84 
28.7 

387 
2.03 
1.45 
1.66 
1.93 
34.6 

3,451 
1.09 
1.24 
0.69 
2.74 
11.9 



SUMMARY AND CONCLUSIONS 



The MIDAS data base stores environ- 
mental data collected from coal mines and 
metal and nonmetal mines or mills. The 
metal and nonmetal data were collected by 
MSHA inspectors from 1974 to the present, 
whereas the coal respirable dust data 
were collected by both coal mine opera- 
tors and MSHA inspectors from 1970 to the 
present. There are about 450,000 records 
from metal and nonmetal mines and mills 
and 6.5 million records from coal mines 
in the data base. 

The data base is split into two subsys- 
tems — metal-nonmetal and coal. The soft- 
ware used to analyze each subsystem is 
similar but not identical because of the 
different record formats and different 
coding systems used in each. The soft- 
ware is user friendly, menu driven, and 
requires minimum knowledge of the central 
computer operating system. Reports are 
in the form of tables and graphs. 

This report also describes results from 
analyses of the metal and nonmetal 
respirable quartz (RQ) data and the coal 
mine respirable dust data gathered by 
MSHA inspectors from 1981 through 1984. 
Major findings of these analyses follow. 

1. There was a reduction in the per- 
centage of samples exceeding the RQ stan- 
dard in metal and nonmetal mines from 
1974 through 1979, and a slight increase 
from 14.7 to 17.2 pet from 1980 through 
1984. This increase was accompanied by 
the collection of fewer samples by MSHA 
and policy changes caused by the passage 
of the 1977 act and changes in the 1982 
appropriation. Overall, 9,000 RQ samples 
(18 pet) exceeded the RQ standard. 

2. The use of respiratory protec- 
tion among metal and nonmetal mine work- 
ers sampled by MSHA increased from 18 pet 
in 1974 to 47 pet in 1984. Occupa- 
tions showing the greatest increase in 
the use of respiratory protection were 
jack stoper driller (20.4 pet increase), 



pneumatic drill operator (20.3 pet in- 
crease), and flotation operator (19.7 pet 
increase). 

3. Baggers in nonmetal mills had the 
highest percent of samples exceeding the 
RQ standard, but showed the m greatest 
overall improvement with an 11-pct reduc- 
tion in overexposure from the 1974-79 
to 1980-84 period. Flotation operator, 
truck driver, and jack stoper driller 
occupations also reduced the percentage 
of samples over the standard by 10 pet or 
more for the same time periods. Three 
occupations, stope miner, motorman, and 
laborer, showed slight increases in the 
percent of overexposures for these two 
time periods. 

4. Analysis of metal and nonmetal RQ 
data collected by MSHA inspectors showed 
that the net effect of changing the cur- 
rent standard from a formula based upon 
the percentage of quartz in the sample to 
a standard of 100 ug/m 3 of respirable 
quartz would be 4 pet fewer samples would 
exceed the standard. 

5. Analysis of coal mine respirable 
dust data showed that between 1981 and 
1984, 10 to 12 pet of the samples ex- 
ceeded the 2.0-mg/m 3 standard while the 
geometric mean concentration (GM CONC) 
fluctuated between 0.59 and 0.69 mg/m 3 . 
On average, about 1,800 samples exceeded 
the standard each year. However, far 
fewer mines were out of compliance be- 
cause compliance is based on the arithme- 
tic average of five samples exceeding the 
2.0-mg/m 3 standard. 

6. Designated occupation concentra- 
tions are generally higher than the non- 
designated occupation values at mines 
using longwall, continuous rippers, or 
augering as the mining method. 

7. Mines with longwall plows or shears 
have the highest GM CONC (1.64 and 1.29 
mg/m 3 ) and the greatest percentage of 
samples exceeding the 2.0-mg/m 3 standard 



(43.7 and 25.2 pet). However, many more 
samples (10,946) were recorded at mines 
using continuous rippers with 10.9 pet of 
the samples exceeding the 2.0-mg/m 3 limit 
with a GM CONC of 0.66 mg/m 5 . The dust 
concentrations were greater at mines with 
longwall operations but there were nearly 
nine times more continuous ripper oper- 
ations with samples having dust concen- 
trations greater than the Federal 
standard. 



8. Coal mine occupations with the 
greatest percent of samples exceeding the 
2.0-mg/m 3 standard were auger jack set- 
ter, longwall shear-plow operator, fine 
coal plant operator, and longwall jack 
setter. Occupations with the greatest 
number of samples exceeding the 2.0-mg/m 5 
standard were continuous miner operator 
and helper, roof bolter, and highwall 
drill operator. 



REFERENCES 



1. National Materials Advisory Board. 
Measurement and Control of Respirable 
Dust in Mines. Natl. Acad. Sci. , Wash- 
ington, DC, NMAB-363, 1980, 405 pp. 

2. U.S. Congress. Federal Mine Safety 
and Health Act of 1977. Public Law 91- 
173, as amended by Public Law 95-164, 
Nov. 9, 1977, 83 Stat. 803. 

3. U.S. Code of Federal Regulations. 
Title 30 — Mineral Resources; Chapter 1 — 
Mine Safety and Health Administration, 
Department of Labor; July 1, 1984. 

4. American Conference of Governmental 
Industrial Hygienists (Cincinnati, OH). 
TLV's — Threshold Limit Values for Chemi- 
cal Substances in Workroom Air Adopted by 
the ACGIH in 1973. 1973, 54 pp. 

5. Watts, W. F., Jr., R. L. Johnson, 
D. J. Donaven, and D. R. Parker. An 
Introduction to the Mine Inspection 
Data Analysis System (MIDAS). BuMines 
IC 8859, 1981, 41 pp. 

6. Sutton, G. W. , G. W. Weeras, L. A. 
Schutz, and G. D. Trabant. Summary Re- 
port of the Environmental Results of the 
MSHA and NIOSH Silica/Diesel Exhaust 
Study. Paper in Industrial Hygiene for 
Mining and Tunneling. Proceedings of a 
Topical Symposium sponsored by ACGIH, 
November 6 and 7, 1978, Denver, CO. 
ACGIH, 1979, pp. 109-117. 

7. Watts, W. F., D. R. Parker, and 
J. E. Small-Johnson. Gas and Dust Con- 
centrations at 18 Underground, Diesel- 
ized, Noncoal Mines. Pres. at Am. Ind. 
Hyg. Assoc. Meet., May 19-24, 1985, 



Las Vegas, NV, 17 pp.; available from 
W. F. Watts, Jr., BuMines, Minneapolis, 
MN. 

8. Dixon, W. J. (ed. ). BMDP Statis- 
tical Software. Univ. CA Press, 1985, 
734 pp. 

9. U.S. Congress. The Federal Mine 
Safety and Health Act of 1977. Public 
Law 91-173, as amended by Public Law 95- 
164, Nov. 9, 1977, 91 Stat. 1291 and 
1299. 

10. Treaftis, H. N. , A. J. Gero, P. M. 
Kacsmar, and T. F. Tomb. Comparison of 
Mass Concentrations Determined With Per- 
sonal Respirable Coal Mine Dust Samplers 
Operating at 1.2 Liters Per Minute and 
the Casella 113A Gravimetric Sampler 
(MRE). Am. Ind. Hyg. Assoc J. , v. 45, 
No. 12, 1984, pp. 826-832. 

11. American Conference of Governmen- 
tal Industrial Hygienists (Cincinnati, 
OH). Documentation of the Threshold 
Limit Values. 4th ed. , 1980, pp. 364- 
365. 

12. U.S. Mine Safety and Health Ad- 
ministration. Preproposal Draft Air 
Quality Standards. 1983, 61 pp. ; avail- 
able from Health Div. for Metal and Non- 
metal Safety and Health, MSHA, Arlington, 
VA. 

13. Watts, W. F., Jr., D. R. Parker, 
R. L. Johnson, and K. L. Jensen. Analy- 
sis of Data on Respirable Quartz Dust 
Samples Collected in Metal and Nonmetal 
Mines and Mills. BuMines IC 8967, 1984, 
28 pp. 



APPENDIX. --MSHA SAMPLING CODES, DESCRIPTORS, AND SELECTED DATA 
TABLE A-l. - Metal and nonmetal occupation codes 



iy 



Code Occupation 

28. . Scoop-tram 

29. . Mucking machine , 

30. . Slusher 

32. . Brattice 

34. . Diamond drill , 

35.. Continuous miner helper..... 

36.. Continuous miner operator.., 

37.. Cutting machine helper , 

38.. Cutting machine operator..., 

39.. Hand loader , 

41.. Jack setter , 

43.. Gather arm loader 

45.. Hand and chute blast 

46.. Rock and roof bolter 

48.. Roof bolter mounted 

53. . Utility man , 

57.. Stope miner , 

58.. Drift miner , 

59. . Raise miner , 

79. . Crusher , 

134. Jet-piercer channel , 

154. Belt cleanup , 

179. Ball and rod mill , 

216. Track gang , 

234. Jet piercer drill , 

261. Battery station , 

279. Hammer mill 

331. Clam-shell 

334. Wagon drill , 

342. Bit grinding and sharpening, 

344. Car shakeout 

352. Iron and metal work 

367. Shovel operator 

368. Bulldozer 

372. Barge and dredge 

375. Road grader 

376. Trucker 

378. Mobile crane 

379. Dryer and kiln 

385. Lampman 

387. Rotary bucket excavation... 

588. Sizing and washing 

601. Conveyor belt 

602. Electrician 

603. Electrician helper 

604. Mechanic 

607 . Jackhammer 

608. Mason 

609. I Supply man nipper 



Samples 



Code 



Occupation Samples 

Belt vulcanizer 

Cleanup man 4,712 

Sampler 27 

Laborer and bullgang.... 571 

Greaser and oiler 61 

Welder 159 

Dump operator 192 

Surveyor 

Rotary drill 74 

Administrator 419 

Machinist 

Shaft miner 3 

Tractor operator 11 

Puller and truck loader. 138 

Leaching operations 14 

Warehouse man 376 

Dragline 11 

Flotation 657 

Scraper-loader 46 

Shotcrete man 

Ventilation crew 1 

Ground control 98 

Cement operations 223 

Grizzly tender 9 

Load, haul, dump cycle.. 123 

Pneumatic drill 1,049 

Hand trammer 4 

Hand scaling 1 

Diesel shuttle 10 

Raise borer 

Shaft repair 

Dry sandfill 14 

Wet sandfill 2 

Backhoe 2 

Pelletizing 350 

Front-end loader 13,463 

Scalper screen 19 

Forklift 28 

Top skip and tipple 5 

Weight and scale 8 

Carpenter 1 

Yard engine 3 

Stone and rock saw 326 

Janitor 2 

Salvage crew 

Aerial tram 1 

Churn drill 4 

Engineer 263 

Hydrating plant 4 



19 

94 

290 



76 

3 

66 



1 

2 

2 

2 



96 

2 

125 

1,248 

80 

7 

8,342 

110 

21 

1,523 

46 

6 



8 

3 

1,634 



6 

1 

97 

1,122 

64 

9 

1,259 

11 

1,982 



1 

1,751 

25 

7 



1,691 

112 



6 



612. 
613. 
614. 
616. 
618. 
619. 
622. 
623. 
634. 
649. 
660. 
663. 
668. 
669. 
673. 
674. 
678. 
679. 
682. 
706. 
708. 
710. 
716. 
726. 
728. 
734. 
739. 
747. 
750. 
759. 
763. 
765. 
766. 
778. 
779. 
782. 
388. 
389. 
392. 
393. 
394. 
397. 
399. 
413. 
416. 
420. 
434. 
456. 
479. 



20 



TABLE A-l. - Metal and nonmetal occupation codes — Continued 



Code 



Occupation 

Dry screen plant.., 
Building repair..., 
Lab technician. 
Tamping machine..., 
Jack stoper drill.. 
Slurry and mix. 

Plumber , 

Powder gang , 

Bobcat , 

Drill helper , 

Mechanical scaling, 



Samples 



Code 



Occupation 

Ramcar , 

Overhead crane 

Bagging and packing..., 

Painter 

Cager 

Hoist , 

Skip tender 

Jumbo percussive drill, 

Electic shuttle 

Trip rider swamper. 
Motorman 



Samples 



488. 
513. 
514. 
516. 
534. 
579. 
804. 
807. 
825. 
833. 
847. 



233 


850. 


29 


878. 


58 


879. 





894. 


675 


920. 


109 


921. 


17 


930. 


36 


934. 


11 


950. 


15 


962. 


4 


969. 





6 

2,745 



4 

148 

17 

50 





1,087 



TABLE A-2. - Metal and nonmetal location codes 



Code 



Location 



Underground: 

1 Active mining. 

3 Exploration and development , 

5 Travel and haul way. 

7 Shaft and station. 

9 Hoistroom. 

11 Ore processing. 

13 Ore transfer point. 

15 Shops. 

17 Office and storeroom. 

19 General. 

21 Construction. 

Surface: 

31 Active mining. 

33 Exploration and development, 

35 Roads. 

39 Tailings pond. 

41 Ore processing. 

43 Ore transfer point. 

45 Shops. 

47 Office and storage. 



Code 



Location 



Surface — Con. 

49 General. 

51 Construction. 

Mill: 

61 Crushing. 

63 Grinding. 

65 Washing and screening. 

67 Dry screening. 

69 Drying and roasting. 

71 Ore transfer point. 

73 Shops. 

75 Office and storage. 

77 General. 

79 Flotation and reagents, 

81 Pelletizing. 

83 Bagging and packing. 

85 Construction. 

Miscellaneous: 

37 Dredges and barges . 

99 Anywhere. 



21 



TABLE A-3. - Metal and nonmetal SIC codes 



Code 



Commodity 



Samples' 



Code 



Commodity 

NONMETAL— Continued: 

Phosphate rock , 

Salt rock , 

Sulfur , 

Chemical fertilizer...., 

Lithium , 

Pigment minerals , 

Pyrites , 

Strontium , 

Gypsum , 

Talc and pyrophylite. . . , 

Nonmetal minerals 

Asbestos 

Gems tones , 

Gilsonite 

Mica 

Peat , 

Perlite , 

Pumi ce , 

Vermiculite , 

Industrial chemicals..., 

Alumina , 

Evaporated salt , 

Brine salt , 

Leonardite , 

STONE 

Other dimension stone.., 

Dimension granite , 

Dimension limestone...., 

Dimension marble , 

Dimension sandstone...., 

Dimension slate 

Dimension traprock 

Crushed limestone 

Crushed granite , 

Crushed stone 

Crushed marble , 

Crushed sandstone 

Crushed slate , 

Crushed traprock 

Cement 

Lime 

SAND AND GRAVEL 

Sand and gravel 

UNKNOWN 

Unknown. 



Samples' 



METAL 



10110 
10210 
10310 
10410 
10440 
10510 
10610 
10611 
10612 
10613 
10614 
10615 
10616 
10617 
10920 
10940 
10941 
10942 
10990 
10991 
10992 
10993 
10994 
10995 
10996 
10997 



13111 
13112 
14530 
14550 
14590 
14591 
14592 
14593 
14594 
14595 
14596 
14720 
14730 
14740 
14741 
14742 
14743 
14744 



Iron 

Copper 

Lead and zinc 

Gold 

Silver 

Aluminum 

Ferroalloy 

Chromite 

Cobalt 

Columbium, tantalum.... 

Manganese 

Molybdenum 

Ni eke 1 

Tungsten 

Mercury 

Uranium and vanadium. . . 

Uranium 

Vanadium 

Other metal 

Antimony 

Beryl 

Platinum 

Rare earths 

Tin 

Titanium 

Zircon 



NONMETAL 



Oil shale 

Oil sand 

Fire clay 

Common clay 

Ceramic clay 

Aplite 

Brucite 

Feldspar. 

Kyanite , 

Magnesite 

Common shale , 

Barite 

Fluorspar , 

Potash, soda, borate. 

Boron , 

Potash , 

Trona , 

Sodium compounds...., 



2,593 

2,240 

1,044 

1,150 

756 

8 





5 



20 

600 

6 

53 

11 

275 

1,158 

6 

34 

37 

4 



23 

1 

8 





102 



784 

2,792 

13 

7 



252 

27 



326 

226 

142 

2 

21 

2 

13 





14750 
14760 
14770 
14790 
14791 
14792 
14793 
14794 
14920 
14960 
14990 
14991 
14992 
14993 
14994 
14995 
14996 
14887 
14998 
28190 
28191 
28991 
28992 
29900 



14110 
14111 
14112 
14113 
14114 
14115 
14116 
14220 
14230 
14290 
14291 
14292 
14293 
14294 
32410 
32740 



14410 



531 

16 





113 

4 





241 

183 

881 

3 

7 

2 

146 



29 

37 

15 



10 





50 



57 

1,113 

259 

35 

434 

260 

58 

13,054 

3,206 

689 

18 

3,421 

94 

869 

1,232 

323 



8 ,309 







68 



For respirable quartz. 



22 



TABLE A-4. - Occupation codes most frequently used in 1984 by MSHA coal 
mine inspectors 



Code 



Occupation 



Samples 



Code 



Occupation 



Samples 



UNDERGROUND FACE 



UNDERGROUND FACE— Continued 



1... 

4... 
7... 
10.. 

16.. 
34.. 
35.. 
36.. 
37.. 
38.. 
39.. 
40.. 
41.. 
43.. 
44.. 
46.. 
47.. 
48.. 
49.. 
50.. 

52.. 
53.. 
54.. 
55.. 



72.. 

T 



Belt man , 

Mechanic. *. , 

Shotf irer , 

Auger jack setter (intake 

side) , 

Laborer , 

Coal drill operator 

Continuous miner helper.., 
Continuous miner operator, 
Cutting machine helper. . . , 
Cutting machine operator., 

Hand loader , 

Headgate operator , 

Longwall jack setter , 

Loading machine operator.. 
Longwall (tailgate side)., 

Roof bolter , 

Roof bolter helper , 

Roof bolter (return side), 

Section foreman , 

Shuttle car operator 

(standard side) , 

Tailgate operator , 

Utiltity man , 

Scoop car operator , 

Auger jack setter (return 

side) , 

Mobile bridge operator..., 



57 
181 

174 

279 

63 

483 

1,405 

2,579 

96 

516 

117 

136 

499 

283 

387 

3,451 

629 

78 

277 

2,123 

71 

304 

938 

116 
136 



73.. 

74.. 



302, 
304. 
310, 
313. 
314. 
316. 
318. 
319, 
367, 
368, 
373, 
374. 
375. 
376. 
378. 
380. 
382. 
383. 
384. 
386. 
388. 
392. 
999. 



Shuttle car operator (off 

standard) 

Motorman 



SURFACE 



Electrician 

Mechanic 

Scraper operator. 

Cleanup man 

Coal sampler 

Laborer 

Oiler-greaser 

Shop welder 

Coal shovel operator 

Bulldozer operator 

Car dropper 

Cleaning plant operator.. 

Road grader operator 

Coal truck driver 

Crane-dragline operator.. 
Fine coal plant operator. 

Highlift operator 

Driller highwall helper.. 
Highwall drill operator.. 

Refuse truck driver 

Scalper-screen operator.. 

Tipple operator 

Not designated 



757 
148 



87 
339 
221 
169 

74 
525 
189 

91 

107 

1,651 

92 
216 

79 

179 

232 

197 

1,565 

57 
817 
634 
108 
375 
1,335 



Respirable coal dust. 



TABLE A-5. - MSHA coal mine codes for mine type 



Code Mine type 

1970-80: 

Surface. 

1 Development. 

2 Retreat. 



Code 



Mine type 



Post-1980: 

A Surface. 

B Underground. 



23 



TABLE A-6. - MSHA coal mine codes for sample type 



Code 



Sample type 



1970-80 inspector and operator: 

Surface. 

1 High risk. 

2 Intake air. 

3 Non-high risk. 

4 Nonf ace. 

5 Part 90 miner. 

Post-1980 inspector: 

1 Designated occupation. 

2 Nondesignated occupation, 

3 Designated area. 

4 Designated work position. 



Code 



Sample type 



Post-1980 inspector — Continued 

5 Part 90 miner. 

6 Nondesignated area. 

7 Intake air. 

8 Nondesignated work position. 

Post-1980 operator: 

1 Mechanized mining unit. 

2 Nondesignated occupation. 

3 Designated area. 

4 Designated work position. 

5 Part 90 miner. 



TABLE A-7. - MSHA coal mine codes for mining method 



Code Mining method 

1970-80: 

1 Continuous. 

2 Conventional. 

3 Longwall. 

4 Other. 

5 Surface. 

Post-1980: 

A Longwall shear. 

B Longwall plow. 

C Continuous ripper. 

D Continuous bore. 

E Continuous auger. 



Code 



Mining method 



Post-1980 — Continued 

F Continuous shortwall. 

G Conventional with cutting 

machine. 

H Scoop with cutting machine. 

I Scoop shoot off solids. 

J Conventional shoot with loading 

machine. 

K Hand load cutting machine. 

L Hand load shoot off solids. 

M Hand load anthracite. 

N Other (surface). 



TABLE A-8. - Percentage of metal and nonmetal miners wearing respirators 



Occupation 


1974-79 


1980-84 


Change 


Occupation 


1974-79 


1980-84 


Change 


Jack stoper drill. . 
Pneumatic drill.... 
Flotation operator. 


38.3 
38.7 
30.3 
30.4 
36.9 
45.8 
26.9 
33.5 
45.4 


58.7 
59.0 
50.0 
49.2 
55.2 
61.6 
41.9 
48.3 
59.9 


20.4 
20.3 
19.7 
18.8 
18.3 
15.8 
15.0 
14.8 
14.5 




25.9 
32.4 
30.7 
60.0 
21.2 
36.9 
18.6 
42.3 


39.9 
46.0 
44.2 
71.4 
31.6 
45.5 
26.4 
47.5 


14.0 


Crusher worker. . . . 


13.6 
13.5 




11.4 


General cleanup.... 
Ball and rod mill.. 


Front-end loader.. 
Sizing and washing 


10.4 
8.6 
7.8 
5.2 






35.0 


49.2 


14.2 



15087 21f 



INT.-BU.OF MINES,PGH.,PA. 28408 



U.S. Department of the Interior 
Bureau of Mines— Prod, and Oistr. 
Cochrans Mill Road 
P.O. Box 18070 
Pittsburgh. Pa. 15236 



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